1. Field of the Invention
The present invention relates to heating devices and in particular to a new and useful heat transfer installation or system with a storage reservoir containing a salt as the heat carrier.
2. Description of the Prior Art
In heat exchange installations, a heat storage reservoir is provided in cases where the amount of heat supply and heat demand differ from each other within a given time. In most instances, the heat energy is available for a shorter period of time, while the heat consumption is more or less continuous. Available sources of heat energy are, for example, night current, solar energy, or heat from industrial processes. As a storage medium, fused salts are provided which are chemically stable even in high temperature ranges.
In prior art installations of this kind, in which fusible salts stable even at high temperatures, i.e. up to about 500.degree. C., are employed as stored heat carriers, it is provided to use the respective available energy for heating up this heat carrier, and the salt is heated, starting from its solid state above the melting point and up to the highest admissible operating temperature, while the removal of heat, for example, by heat exchange to produce hot water for heating or other consumption purposes, by which the heat carrier is cooled down, is continued to below the freezing point of the fused salt. In eutectic compositions, fused salts have a melting point in the range of about 150.degree. C., so that their cooling down, for example, to 120.degree. C. is still quite acceptable, even for producing hot water. This means, however, that between the consecutive heating-up periods, the heat carrying salt must each time pass from its liquid into its solid state (and inversely), which results in uncontrollable mechanical stresses in the storage system.